One other thing to remember is that most, if not all, sites have TOS rules about abusing their bonuses (which I, personally, support them having). So if you do find a 100% bonus, deposit $50, get $50 free, then withdraw your initial $50, don't be a bit surprised when then immediately take your $50 bonus away.
Bonuses are given as marketing tools and the sites don't take kindly to people abusing their "generosity". And they are within their rights to do so. And as far as abuse goes, that is typically within their discretion alone. So, instead of trying to get something for nothing, why not put some money in, get the bonus, and work on improving your game so you can stop constantly depositing and/or trying to constantly get extra free bonus money. A good player will make more money playing than someone that runs around trying to scam bonuses.